Modern electrophotographic printers are complex machines that use a significant number of electromechanical devices, such as solenoids, electric motors, and relays to provide force responses. Such devices are subject to both mechanical and electrical degradation. Since low down time is critical, in the event of machine failure rapid diagnoses and repair of such printers is very important. Ideally, field service representatives would have an ability to anticipate problems so that corrective action could be taken before actual failure.
Diagnosing some electromechanical devices, in particular electric motors, using analog current signature analysis is well known. Such analysis is performed by monitoring the electrical current into a device being tested, comparing that current to a current baseline, and then determining whether the device being tested is acceptable. While beneficial, analog current signature analysis has been limited to situations where ready access is available to the device being tested.
Unfortunately, with most electrophotographic printers access to most electromechanical devices is severely limited. This precludes easy testing. Additionally, even when accessible, most electromechanical devices are not easily tested during operation since device power is applied only for short periods of time commanded by a microprocessor. Since an electromechanical device being tested might not be powered until a prior operation is performed by another electromechanical device that is controlled by another microprocessor, a very complex synchronization scheme might be required to simply test one electromechanical device.
Because of their complexity modern, high speed electrophotographic printers are often divided into discrete modules (subsystems) that intercommunicate with a master controller via a serial control bus. A typical bus might include a transmit line (Tx), a receive line (Rx), a clock line (Clk), a return line (Return) and a power line. The transmit, receive, clock, and return lines provide digital control while the power line and the return line provide power distribution.
Therefore, the ability to field-service test modular, digital-bus controlled electrophotographic printers using analog current analysis of power devices would be beneficial.